Although the principles offered here may relate to any sterilization system where high-temperature steam is used, for sake of convenience we will refer almost exclusively to an ambulatory autoclave (e.g., for use in dental and veterinary clinics, for tattoo artists and beauticians), but it is to be understood that this does not limit the scope of the application of the invention.
In medical clinics, particularly in dental clinics, it has long been known that small size autoclaves are used to sterilize small manual tools or dental handpieces. The autoclaves usually have a sterilization chamber, which is for the most part empty and provided with appropriate equipment (such as baskets, trays or storage compartments) to house the devices to be sterilized (i.e. the workload). The chamber is provided with an opening to introduce the load and can be tightly closed (sealed) to carry out the desired sterilization cycle.
The sterilization process takes place according to typical cycles, often compliant with a standard, with the aid of equipment and operation devices for the sterilization chamber. Typically, even if this should not be considered as a limitation, the following devices are provided:                a pair of water tanks, one for clean water, which is picked up to produce the steam and one for waste (used) water, deriving from the condensation of the steam;        a pump to move the water;        a steam generator, in which clean water is injected to produce the steam that acts as a working fluid;        a condenser, to carry out the steam condensation and its related discharge towards the collection waste tank;        a vacuum pump, intended to empty the sterilization chamber;        and a series of electrovalves and ducts to put the equipments and devices in communication each other in the desired modes and times.        
An exemplary autoclave of this type is known from EP 992.247, whose circuit scheme is shown in FIG. 1 as an example of prior art.
A sterilization process normally involves—after the autoclave loading and its sealing—an emptying cycle of the sterilization chamber air, a pressurization cycle of the chamber with high temperature (about 120°-145° C.) and pressure (up to about 2-3 bar) steam and finally an emptying cycle of the chamber and subsequent drying. In the pressurization cycle, the actual sterilization of the tools takes place inside the chamber, while the final phase of emptying and drying is used to ensure a perfect drying of the tools for their proper preservation.
This general operation process is an example of what actually takes place, because there are many operation variations to achieve a greater efficiency of the process and optimal energy yields.
One of the most critical and expensive components in an autoclave is the vacuum pump, which is used to achieve the emptying of the sterilization chamber. This device, besides involving a cost, often causes problems, both because it has moving elements—therefore subject to wear and/or fatigue—and because it treats a fluid (steam) that can undergo changes in status (from gaseous to liquid) with inevitable associated problems (due to the biphasic flow).
In the past, it has already been proposed to produce vacuum in the sterilization system using fluids, rather than a vacuum pump. For example GB 1137409 describes a sterilization system where a complex hydraulic circuit is used with related water tanks, in order to obtain a pressure reduction. However, the system is complex and difficult to implement and control.
GB 993.883 discloses another autoclave system where a generator is connected both to the sterilization chamber and to a condenser immersed in a water tank. This configuration is intended to regulate the water level in the generator to prevent the heating elements from being exposed, but does not provide any fluid-dynamic interaction between the generator and the condenser. DE102012010739 shows another autoclave system, wherein a condenser is partly in communication with a steam generator, but the evacuation of the sterilization chamber is still determined by vacuum pumps. WO00/59553 and EP852146 illustrate other autoclave configurations with sterilization cycles which still only use vacuum pumps to evacuate the sterilization chamber. EP 992.247 owned by the same applicant, describes a further autoclave circuit wherein a separated small cold lung of the system is used to cooperate in the emptying of the sterilization chamber.
The applicant has the aim of providing a sterilization system and a related operation process, which could achieve a good operation of the sterilization cycle and in particular the emptying of the sterilization chamber, eliminating or reducing the contribution of a vacuum pump and modifying to the minimum necessary the existing circuits for traditional autoclaves provided with vacuum pump.